Porous, sound-absorbing ceramic moldings and method for production thereof

ABSTRACT

The present invention is a porous sound-absorbing ceramic form made of a porous ceramic material with communicating pores and having a bulk specific gravity of 0.5 to 1.0. The porous ceramic material consists essentially of 100 parts by weight of perlite having a particle diameter of 0.50 to 2.0 mm, 100 to 200 parts by weight of at least one sintered material selected from the group consisting of fly ash, chamotte, wollastonite, slag, silica, volcanic ejecta, rock, and clay mineral as a matrix material, and 10 to 20 parts by weight of an inorganic binder, which have been sintered so that the matrix material, together with the binder, surrounds the perlite particles. The perlite particles form communicating openings at mutually contacting portions thereof, so that the internal pores are communicating pores. 
     The present invention provides low-cost porous sound-absorbing ceramic forms, such as sound-absorbing bricks and tiles, which exhibit excellent sound-absorbing characteristics over a wide frequency range from low frequencies to high frequencies.

This application is a 371 of PCT/JP01/09108, filed Oct. 17, 2001.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to porous sound-absorbing ceramic formssuch as porous sound-absorbing bricks, tiles and other plate-shapedmaterials produced from perlite as a main raw material. The presentinvention also relates to a method of producing such poroussound-absorbing ceramic forms.

BACKGROUND ART

Sound-absorbing materials constituting soundproofing walls used forroads, buildings, etc. are demanded to absorb sound in the frequencyrange of 400 to 4000 Hz, which human beings are likely to feel to be aloud noise. It is particularly demanded to absorb sound in the frequencyrange of 800 to 2000 Hz.

Sound-absorbing materials containing mineral fiber such as glass wool orrock wool have heretofore been known as typical sound-absorbingmaterials. The mineral fiber-containing sound-absorbing materialssuffer, however, from some disadvantages. That is, when the mineralfiber-containing sound-absorbing materials contain water, thesound-absorbing performance is markedly degraded. In addition, becausethey are made of fibers, the mineral fiber-containing sound-absorbingmaterials may become deformed with time and are likely to be scatteredor peeled off by a high-speed air stream. Further, the resin materialcontained as a binder may be deteriorated by ultraviolet rays.

To overcome the disadvantages, the conventional practice is to cover themineral fiber-containing sound-absorbing materials with resin films andto accommodate them in metallic containers. However, this causes thecost to increase considerably.

A sound-absorbing material consisting of gypsum board provided with alarge number of through-holes is also well known. However, thesound-absorbing material consisting of perforated gypsum board has thefollowing problem. The gypsum board does not have sound-absorbingperformance but absorbs sound energy by resonance in the through-holes.Therefore, the sound-absorbing material can absorb sound only atspecific frequencies. To solve this problem, the conventional practiceis to provide an air layer at the back of the gypsum board or to installa backing material, e.g. glass wool, on the back of the gypsum board.These methods, however, require a great deal of time and labor forconstruction.

Meanwhile, ceramic tiles and bricks made by firing silicate mineralshave heretofore been used as building materials, furnace materials andso forth. Moreover, various ceramic materials are being used for noisecontrol measures in urban and industrial environments.

However, low-cost ceramic materials having excellent sound-absorbingqualities have not yet been provided, and hence no reduction in the costof construction has yet been attained.

DISCLOSURE OF THE INVENTION

In view of the above-described conventional circumstances, the presentinvention provides low-cost porous sound-absorbing ceramic forms, suchas sound-absorbing bricks and tiles, which have good weatherability andexhibit excellent sound-absorbing characteristics over a wide frequencyrange from low frequencies to high frequencies which human beings feelto be a loud noise.

That is, the present invention provides porous sound-absorbing ceramicforms and methods of producing the same, which have the followingstructures and arrangements.

(1) A porous sound-absorbing ceramic form made of a porous ceramicmaterial with communicating pores and having a bulk specific gravity of0.3 to 1.5, wherein the porous ceramic material consists essentially of100 parts by weight of perlite having a particle diameter of 0.10 to 8.0mm, 80 to 250 parts by weight of at least one sintered material selectedfrom the group consisting of fly ash, slag, silica, volcanic ejecta,rock, and clay mineral as a matrix material, and 5 to 30 parts by weightof an inorganic binder, which have been sintered so that the matrixmaterial, together with the binder, surrounds the perlite particles, andwherein the perlite particles form communicating openings at mutuallycontacting portions thereof, so that the internal pores arecommunicating pores.

(2) A porous sound-absorbing ceramic form made of a porous ceramicmaterial with communicating pores and having a bulk specific gravity of0.5 to 1.0, wherein the porous ceramic material consists essentially of100 parts by weight of perlite having a particle diameter of 0.50 to 2.0mm, 100 to 200 parts by weight of at least one sintered materialselected from the group consisting of fly ash, chamotte, wollastonite,slag, silica, volcanic ejecta, rock, and clay mineral as a matrixmaterial, and 10 to 20 parts by weight of an inorganic binder, whichhave been sintered so that the matrix material, together with thebinder, surrounds the perlite particles, and wherein the perliteparticles form communicating openings at mutually contacting portionsthereof, so that the internal pores are communicating pores.

(3) A porous sound-absorbing ceramic form made of a porous ceramicmaterial with communicating pores and having a bulk specific gravity of0.5 to 1.0, a bending strength of 10 to 28 kgf/cm² and a compressivestrength of 40 to 90 kgf/cm², wherein the porous ceramic materialconsists essentially of 100 parts by weight of perlite having a particlediameter of 0.50 to 2.0 mm, 100 to 200 parts by weight of sintered flyash as a matrix material, and 10 to 20 parts by weight of an inorganicbinder, which have been sintered so that the matrix material, togetherwith the binder, surrounds the perlite particles, and wherein theperlite particles form communicating openings at mutually contactingportions thereof, so that the internal pores are communicating pores.

(4) A porous sound-absorbing ceramic form as stated in any one of theabove paragraphs (1) to (3), wherein the perlite is one obtained byfire-expanding ground pearlite, obsidian or pitchstone.

(5) A porous sound-absorbing ceramic form as stated in any one of theabove paragraphs (1) to (4), wherein the matrix material contains 10 to50 parts by weight of glass.

(6) A porous sound-absorbing ceramic form as stated in any one of theabove paragraphs (1) to (5), wherein the perlite and/or the matrixmaterial has been crystallized by addition of a nucleation agent forcrystallization.

(7) A porous sound-absorbing ceramic form as stated in any one of theabove paragraphs (1) to (6), wherein the matrix material furthercontains 1 to 10 parts by weight of at least one short fiber materialselected from the group consisting of metallic fiber, glass fiber,carbon fiber, ceramic fiber, mineral fiber, and whisker.

(8) A porous sound-absorbing ceramic form as stated in any one of theabove paragraphs (1) to (7), which is brick.

(9) A porous sound-absorbing ceramic form as stated in any one of theabove paragraphs (1) to (7), which is tile of other plate-shapedmaterial.

(10) A method of producing a porous sound-absorbing ceramic form made ofa porous ceramic material with communicating pores and having a bulkspecific gravity of 0.3 to 1.2, the method including the steps of:mixing together 100 parts by weight of perlite having a particlediameter of 0.10 to 3.5 mm, 100 to 250 parts by weight of at least onepowder selected from the group consisting of fly ash, chamotte,wollastonite, slag, silica, volcanic ejecta, rock, sludge, and claymineral, 5 to 30 parts by weight of a binder, and 10 to 50 parts byweight of water; forming the resulting mixture into a predeterminedshape, followed by drying; and firing the mixture at 900 to 1200° C.

(11) A method of producing a porous sound-absorbing ceramic form made ofa porous ceramic material with communicating pores and having a bulkspecific gravity of 0.5 to 1.2, the method including the steps of:mixing together 100 parts by weight of perlite having a particlediameter of 0.50 to 2.0 mm, 35 to 60 parts by weight of at least onepowder selected from the group consisting of fly ash, chamotte,wollastonite, slag, silica, volcanic ejecta, rock, sludge, and claymineral, 10 to 25 parts by weight of a binder, and 20 to 45 parts byweight of water; pressing the resulting mixture in a frame mold with apredetermined shape under a pressure of 8 to 15 kgf/cm², followed bydrying; and firing the mixture at 950 to 1150° C.

(12) A method of producing a porous sound-absorbing ceramic form made ofa porous ceramic material with communicating pores and having a bulkspecific gravity of 0.5 to 1.0, a bending strength of 15 to 28 kgf/cm²and a compressive strength of 40 to 90 kgf/cm², the method including thesteps of: mixing together 100 parts by weight of perlite having aparticle diameter of 0.50 to 2.0 mm, 35 to 60 parts by weight of flyash, 10 to 25 parts by weight of a binder, and 20 to 45 parts by weightof water; pressing the resulting mixture in a frame mold under apressure of 8 to 15 kgf/cm², followed by drying; and firing the mixtureat 950 to 1150° C.

(13) A method of producing a porous sound-absorbing ceramic form asstated in any one of the above paragraphs (10) to (12), wherein thebinder is water glass.

(14) A method of producing a porous sound-absorbing ceramic form asstated in any one of the above paragraphs (10) to (13), wherein anucleation agent for crystallization of glass is added to the mixture.

(15) A method of producing a porous sound-absorbing ceramic form asstated in the above paragraph (14), wherein an annealing treatment forpromoting the crystallization of glass is performed after the firing ofthe body.

(16) A method of producing a porous sound-absorbing ceramic form asstated in any one of the above paragraphs (10) to (15), wherein thebinder contains an organic binder.

(17) A method of producing a porous sound-absorbing ceramic form asstated in any one of the above paragraphs (10) to (16), wherein the bodyis formed by further adding 5 to 10 parts by weight of at least oneselected from the group consisting of metallic fiber, glass fiber,carbon fiber, ceramic fiber, mineral fiber, organic fiber and whisker to100 parts by weight of fly ash powder having a particle diameter of 5 to50 μm.

(18) A method of producing a porous sound-absorbing ceramic form asstated in any one of the above paragraphs (10) to (17), wherein theporous sound-absorbing ceramic form is brick.

(19) A method of producing a porous sound-absorbing ceramic form asstated in any one of the above paragraphs (10) to (17), wherein theporous sound-absorbing ceramic form is tile of other plate-shapedmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the sound-absorbing characteristics of poroussound-absorbing bricks obtained by an example of the present invention.

FIG. 2 is an enlarged view illustrating the external appearance of aporous sound-absorbing ceramic form obtained by an example of thepresent invention.

FIG. 3 is an enlarged sectional view illustrating a poroussound-absorbing ceramic form obtained by an example of the presentinvention.

EXPLANATION OF REFERENCE NUMERALS

1: perlite

2: fly ash

3: communicating openings between perlite particles

4: gaps formed between perlite particles

5: fine gaps formed between fly ash particles in matrix

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below.

Perlite used as a main raw material in the invention of this applicationis generally obtained by firing ground obsidian, pearlite, pitchstone orthe like at about 850 to 1100° C. When heated, such ground material isexpanded into hollow spherical particles by the pressure of gasificationof mainly the water content. Because it is a silica-alumina ceramicmaterial, perlite has considerably high refractoriness despite itslightweight structure. Perlite also has high mechanical strength incomparison to glass balloons and the like. It should be noted thatfoamed shirasu may be used in place of perlite.

Fly ash, chamotte, wollastonite, slag, silica, volcanic ejecta, rock,and clay mineral, which may be used as a raw material of the matrixmaterial, all become sintered materials having considerably highrefractoriness and mechanical strength upon firing. Accordingly, poroussound-absorbing ceramic forms resulting from these materials provideproducts having sufficiently high refractoriness to withstand a fire andlike.

For example, fly ash is the residual ash from the combustion of coal,petroleum pitch, etc., which is discharged in large quantities fromthermal power plants and so forth. There are few available techniques ofutilizing fly ash, and the amount of fly ash used is small. Therefore,the utilization of fly ash is presently examined exhaustively in variousfields. Above all, a fine fly-ash powder having a particle diameter of 5to 50 μm is preferably used.

For example, fly ash has a composition consisting essentially of 50 to68% of SiO₂, 20 to 35% of Al₂O₃, 2 to 7% of Fe₂O₃, 0.6 to 7% of CaO, 0.2to 2% of MgO, 0.1 to 2% of Na₂O, 0.3 to 1.5% of K₂O, and 2 to 4% ofIg.loss. The fly ash is amorphous, and each fly-ash particle is a hollowspherical particle having a diameter of 5 to 50 μm.

Accordingly, the fly-ash particles has excellent rollability andsuperior packability and also exhibits excellent sinterability.

In the production of porous sound-absorbing ceramic forms according tothe invention of this application, first, perlite particles are mixedwith fine fly-ash powder or the like to impart formability, and a smallamount of binder, e.g. cornstarch, CMC, or water glass, is added to themixture. Thereafter, the mixture is pressed into a desired shape, e.g.brick or tile.

It should be noted that the binder used for the pressing process isusually an organic binder, e.g. cornstarch, CMC, sodium alginate, PVA, apolyacrylic emulsion, or a polyhydric alcohol wax. However, an inorganicmaterial gel, e.g. water glass or alumina gel, is preferably used as abinder also serving as a sintering agent for sintering perlite andfly-ash particles, by way of example. It should be noted that a mixtureof water glass, silica gel or alumina gel as an inorganic binder and asmall amount of fine glass powder is also usable as a preferred binder.

In addition, it is preferable to add a nucleation agent forcrystallizing the glassy phase to further increase the strength. It ispossible to use a publicly known nucleation agent used in the productionof crystallized glass, e.g. fluorite, silver, gold, titania, orzirconia.

When the crystallization agent is added in the production process,temperature control should be performed during cooling after firing byan annealing treatment according to a cooling temperature pattern forproducing favorable crystallization in accordance with the conventionalmethod.

Consequently, porous sound-absorbing ceramic forms having markedlyincreased product strength are provided.

Further, it is possible in the present invention to add various fibers,e.g. metallic fiber, glass fiber, carbon fiber, various kinds of ceramicfibers, or whisker for the purpose of reinforcement and electromagneticwave absorption.

Regarding the particle size of raw materials used in the invention ofthis application, the raw materials are preferably in the form of finelydivided powder. That is, the particle diameter of fly ash is preferablyin the range of 5 to 50 μm. The particle diameter of wollastonite(calcium silicate) is preferably in the range of 40 to 70 μm. Theparticle diameter of fine blast furnace slag powder is preferably in therange of 10 to 100 μm. The particle diameter of fine silica powder ispreferably not larger than 1 μm.

In particular, a binder containing water glass (aqueous sodium silicatesolution) promotes greatly the dissolution and gelation of the particlesurfaces of the fly-ash powder material and exhibits the action offirmly sintering the powder particles to each other as the sinteringtemperature rises while thoroughly wrapping the particles. Thus, thebinder serves as a firm bonding component for forming a ceramic bodymanifesting sufficiently high strength at a firing temperature of 850 to1200° C.

For the adjustment of the viscosity of the binder containing waterglass, it is preferable to add clay mineral, e.g. fine kaolin powder, tothe binder.

EXAMPLES

Examples of the production of porous sound-absorbing bricks as poroussound-absorbing ceramic forms according to an example of the presentinvention will be described below.

Example 1

[Raw Materials Used] A. Perlite (fire-expanded obsidian particles; 100parts by weight average particle diameter: 1.5 mm) B. Fly ash (averageparticle diameter: 20 μm) 167 parts by weight C. Water glass (Baumédegree: 36°; specific  67 parts by weight gravity: 1.333)

[Production Process]

In the production of porous sound-absorbing bricks according to thepresent invention: (1) the body for forming was prepared from theabove-described raw materials; (2) the body was formed into a brickshape; (3) the green body was dried; and (4) the dried green body wasfired to produce a porous sound-absorbing brick.

(1) In the preparation of the body for forming, first, 55.7 parts byweight of fly ash (B) was added to 100 parts by weight of perlite (A;total weight), and the raw materials were mixed together for 2 minutesin a concrete mixer.

(a) While the above-described mixing was continued (for 2 minutes), 22.3parts by weight of water glass (C) was sprayed over the mixture to forma granular material having an average particle diameter of 1.7 mm, inwhich fly ash adhered to the surfaces of perlite particles (i.e. theperlite particle surfaces were covered with fly ash and water glass).

(b) While the mixing was further continued (for 2 minutes), 55.7 partsby weight of fly ash (B) was added onto the granules and 22.3 parts byweight of water glass (C) was sprayed thereover to form a granularmaterial having an average particle diameter of 1.9 mm, in which fly ashfurther adhered to the surfaces of the granules obtained at the abovestep (a).

(c) While the mixing was further continued (for 2 minutes), 55.7 partsby weight of fly ash (B) was added onto the granules and 22.3 parts byweight of water glass (C) was sprayed thereover to form a granularmaterial having an average particle diameter of 2.1 mm, in which fly ashadhered to the surfaces of the perlite granules obtained at the abovestep (b). The water content of the granular material obtained by thisprocess was 13%. Accordingly, the granular material was usable as thebody for semi-dry forming.

(2) In the forming process, the body of the granular material obtainedas stated above was cast into molds and pressed under 10 kgf/cm² toobtain brick-shaped green bodies.

(3) In the drying process, the above-described green bodies were driedin a drying oven for 3 hours at 55° C. The dried green bodies wererough-cut at the edges thereof.

(4) Thereafter, the green bodies were heated in a kiln for firing at aheating rate of 2.1 to 2.3° C./min. and maintained at 750° C. for 2.5hours. Thereafter, the temperature was raised to 1100° C., and the greenbodies were maintained at this temperature for 3 hours. Thereafter, thefired bodies were slowly cooled down to 600° C. at a cooling rate of 4°C./min. and further down to 400° C. at 3° C./min. and then allowed tocool down to room temperature.

[Characteristics of Products]

The fired bodies obtained through the cooling process were lightweightand porous products with open pores and substantially no closed pores,which had a compressive strength of 42.0 kgf/cm², a bending strength of14.6 kgf/cm² and a bulk specific gravity of 0.7.

The sound-absorbing characteristics of the porous sound-absorbing bricksproduced by the above-described method were measured. The results of themeasurement are shown in FIG. 1. Bricks having a thickness of 114 mmwere used as specimens. FIG. 1 shows the measured values concerning abrick without a back air layer (0 mm) and a brick with a back air layer(50 mm).

As shown in FIG. 1, the reverberant absorption coefficient at ⅓ octaveband center frequencies of 125 to 4000 Hz assumed high values of 0.75 to0.8 in a low frequency region of 125 to 250 Hz even if no back air layerwas provided. The reverberant absorption coefficient assumed highnumerical values of 0.75 to 0.9 over a wide frequency range of 125 to4000 Hz.

The conventional practice is to increase the back air layer in size inorder to increase the sound absorption coefficient. However, the poroussound-absorbing brick according to the present invention has been provedto be usable as a sound-absorbing material exhibiting excellentsound-absorbing characteristics over a wide frequency range from lowfrequencies to high frequencies without the need of a back air layer.

FIGS. 2 and 3 show the grain structure and the condition ofcommunicating pores of the porous sound-absorbing brick (poroussound-absorbing ceramic form) produced by the above-described method.

FIG. 2 is an enlarged view illustrating the external appearance of theporous sound-absorbing ceramic form, and FIG. 3 is an enlarged sectionalview illustrating the porous sound-absorbing ceramic form. As shown inthe figures, perlite particles 1 are surrounded by a matrix comprisingsintered fly ash 2 accompanied by a binder. Moreover, the perliteparticles 1 communicate with each other through communicating openings3.

It is surmised that the communicating openings 3 are formed as follows.As the perlite particles 1 are heated, the pressure of water vapor andother gas in the hollow insides of the perlite particles 1 increases.When the perlite particles 1 reach a high temperature close to thesoftening point or melting point thereof, the walls of the perliteparticles 1 are broken through by the gas pressure at mutuallycontacting portions of the perlite particles 1. As a result,communicating openings 3 are formed. The temperature at which suchcommunicating openings are formed depends on the kind of perlite.However, it is preferably in the range of 900° C. to 1200° C.,particularly preferably in the range of 1000° C. to 1150° C.

Communicating pores are formed by (1) communicating openings 3 betweenperlite particles 1, (2) gaps 4 formed between perlite particles 1, and(3) fine gaps 5 formed between fly-ash particles in the matrix.

Example 2

In this example of the invention, porous sound-absorbing bricks wereproduced in the same way as in Example 1. This example differs fromExample 1 in that fine blast furnace slag powder was used as a rawmaterial in place of fly ash, and the maximum firing temperature was setat 1120° C. for 3 hours instead of 1100° C. for 3 hours.

The sound-absorbing characteristics of porous sound-absorbing bricksobtained in this example were substantially the same as those of theporous sound-absorbing bricks obtained in Example 1. However, thecompressive strength was slightly higher than in Example 1.

Example 3

In this example of the invention, porous sound-absorbing bricks wereproduced in the same way as in Example 1. This example differs fromExample 1 in that a fine powder obtained by mixing together 80 parts byweight of fly ash (average particle diameter: 20 μm) and 20 parts byweight of fine blast furnace slag powder was used as the raw material B,and firing was performed at 1100° C. for 2 hours. As a result, thesound-absorbing characteristics of porous sound-absorbing bricksobtained in this example were substantially the same as those of theporous sound-absorbing bricks obtained in Example 1.

What is claimed is:
 1. A porous sound-absorbing ceramic form made of aporous ceramic material with communicating pores and having a bulkspecific gravity of 0.3 to 1.5, wherein the porous ceramic materialconsists essentially of 100 parts by weight of perlite having a particlediameter of 0.10 to 8.0 mm, 80 to 250 parts by weight of at least onesintered material selected from the group consisting of fly ash, slag,silica, volcanic ejecta, rock, and clay mineral as a matrix material,and 5 to 30 parts by weight of an inorganic binder, which have beensintered so that the matrix material, together with the binder,surrounds perlite particles, and wherein said perlite particles formcommunicating openings at mutually contacting portions thereof, so thatinternal pores are communicating pores.
 2. A porous sound-absorbingceramic form made of a porous ceramic material with communicating poresand having a bulk specific gravity of 0.5 to 1.0, wherein the porousceramic material consists essentially of 100 parts by weight of perlitehaving a particle diameter of 0.50 to 2.0 mm, 100 to 200 parts by weightof at least one sintered material selected from the group consisting offly ash, chamotte, wollastonite, slag, silica, volcanic ejecta, rock,and clay mineral as a matrix material, and 10 to 20 parts by weight ofan inorganic binder, which have been sintered so that the matrixmaterial, together with the binder, surrounds perlite particles, andwherein said perlite particles form communicating openings at mutuallycontacting portions thereof, so that internal pores are communicatingpores.
 3. A porous sound-absorbing ceramic form made of a porous ceramicmaterial with communicating pores and having a bulk specific gravity of0.5 to 1.0, a bending strength of 10 to 28 kgf/cm² and a compressivestrength of 40 to 90 kgf/cm², wherein the porous ceramic materialconsists essentially of 100 parts by weight of perlite having a particlediameter of 0.50 to 2.0 mm, 100 to 200 parts by weight of sintered flyash as a matrix material, and 10 to 20 parts by weight of an inorganicbinder, which have been sintered so that the matrix material, togetherwith the binder, surrounds perlite particles, and wherein said perliteparticles form communicating openings at mutually contacting portionsthereof, so that internal pores are communicating pores.
 4. A poroussound-absorbing ceramic form according to claim 1, wherein the perliteis one obtained by fire-expanding ground pearlite, obsidian orpitchstone.
 5. A porous sound-absorbing ceramic form according to claim1, wherein the matrix material contains 10 to 50 parts by weight ofglass.
 6. A porous sond-absorbing ceramic form according to claim 1,wherein at least one of the perlite and the matrix material has beencrystallized by addition of a nucleation agent for crystallization.
 7. Aporous sound-absorbing ceramic form according to claim 1, wherein thematrix material further contains 1 to 10 parts by weight of at least oneshort fiber material selected from the group consisting of metallicfiber, glass fiber, carbon fiber, ceramic fiber, mineral fiber, andwhisker.
 8. A porous sound-absorbing ceramic form according to claim 1,which is brick.
 9. A porous sound-absorbing ceramic form according toclaim 1, which is tile of other plate-shaped material.
 10. A method ofproducing a porous sound-absorbing ceramic form made of a porous ceramicmaterial with communicating pores and having a bulk specific gravity of0.3 to 1.2, said method comprising the steps of: mixing together 100parts by weight of perlite having a particle diameter of 0.10 to 3.5 mm,100 to 250 parts by weight of at least one powder selected from thegroup consisting of fly ash, chamotte, wollastonite, slag, silica,volcanic ejecta, rock, sludge, and clay mineral, 5 to 30 parts by weightof a binder, and 10 to 50 parts by weight of water; forming a resultingmixture into a predetermined shape, followed by drying; and firing saidmixture at 900 to 1200° C.
 11. A method of producing a poroussound-absorbing ceramic form made of a porous ceramic material withcommunicating pores and having a bulk specific gravity of 0.5 to 1.2,said method comprising the steps of: mixing together 100 parts by weightof perlite having a particle diameter of 0.50 to 2.0 mm, 35 to 60 partsby weight of at least one powder selected from the group consisting offly ash, chamotte, wollastonite, slag, silica, volcanic ejecta, rock,sludge, and clay mineral, 10 to 25 parts by weight of a binder, and 20to 45 parts by weight of water; pressing a resulting mixture in a framemold with a predetermined shape under a pressure of 8 to 15 kgf/cm²,followed by drying; and firing said mixture at 950 to 1150° C.
 12. Amethod of producing a porous sound-absorbing ceramic form made of aporous ceramic material with communicating pores and having a bulkspecific gravity of 0.5 to 1.0, a bending strength of 15 to 28 kgf/cm²and a compressive strength of 40 to 90 kgf/cm², said method comprisingthe steps of: mixing together 100 parts by weight of perlite having aparticle diameter of 0.50 to 2.0 mm, 35 to 60 parts by weight of flyash, 10 to 25 parts by weight of a binder, and 20 to 45 parts by weightof water; pressing a resulting mixture in a frame mold under a pressureof 8 to 15 kgf/cm², followed by drying; and firing said mixture at 950to 1150° C.
 13. A method of producing a porous sound-absorbing ceramicform according to claim 10, wherein the binder is water glass.
 14. Amethod of producing a porous sound-absorbing ceramic form according toclaim 10, wherein a nucleation agent for crystallization of glass isadded to the mixture.
 15. A method of producing a porous sound-absorbingceramic form according to claim 14, wherein an annealing treatment forpromoting the crystallization of glass is performed after firing of thebody.
 16. A method of producing a porous sound-absorbing ceramic formaccording to claim 10, wherein the binder contains an organic binder.17. A method of producing a porous sound-absorbing ceramic formaccording to claim 10, wherein the body is formed by further adding 5 to10 parts by weight of at least one selected from the group consisting ofmetallic fiber, glass fiber, carbon fiber, ceramic fiber, mineral fiber,organic fiber and whisker to 100 parts by weight of fly ash powderhaving a particle diameter of 5 to 50 μm.
 18. A method of producing aporous sound-absorbing ceramic form according to claim 10, wherein theporous sound-absorbing ceramic form is brick.
 19. A method of producinga porous sound-absorbing ceramic form according to claim 10, wherein theporous sound-absorbing ceramic form is tile of other plate-shapedmaterial.